From what was a fairly dominant position, the latest opinion polls will concern Hillary Clinton's presidential campaign.

She is now tied with Donald Trump in Florida, down in Ohio and slightly ahead in Pennsylvania - all states anyone who wants to win the White House really has to take.

While it remains difficult for Trump to get what he needs to secure victory, there are five reasons to believe he may win.

LATEST POLL FIGURES: Clinton vs Trump

National: 45.6/42.9

Florida: 44.8/44.5

Ohio: 43.7/42.7

Pennsylvania: 46.8/40.6

Source: RealClearPolitics average of national polls

1. Trump has consistently confounded expectations: Throughout the primary campaign we were told there was no way he would win the Republican nomination. He was too unlikeable, too abrasive; he had no political operation to speak of. It didn’t matter. He crushed the campaigns of 16 others, many of whom had been planning their assault on the White House for years. Many people like him because he is outspoken and outrageous. He’s seen as something different from the politics and the politicians many feel have failed them. And while he may carry the tag Republican, some of his positions have appeal to disgruntled Democrats.

2. The race is tightening: The bump Clinton received from what was perceived as a successful convention was never going to last. After the Labour Day holiday, which traditionally marks the end of the summer in the US, people start paying more attention to November's election. Here's another thing to consider: It's just over a week since Trump really started airing TV ads in support of his campaign. The Clinton campaign has blanketed the airwaves in the crucial swing states, spending millions of dollars. And still she hasn't been able to pull away and create a gap big enough to put the election to bed.

3. Turnout: Trump doesn't have a great on-the-ground operation in important swing states, but the Republican Party does. And it has scared voters worried that a low turnout will mean Republicans losing control of both the Senate and possibly even the House of Representatives. That will inspire voters to make their way to the polls. The Democrats' get-out-the vote operation is considered more advanced and more sophisticated, but fear is an incredible motivator.

4. People don't trust Clinton: The Democratic candidate hoped to have put her email scandal behind her by now. So many times her campaign has reacted to the latest story on her use of a private server with "Nothing new here, let's move on", but it hasn't worked. She would be the most unpopular candidate ever to run in a presidential election, if she wasn't up against Trump. She still has to convince Bernie Sanders supporters that she shares their aims and goals and will adopt at least part of his agenda if she wins the White House. She has enthusiastic supporters, of that there's no doubt, but she doesn't energise the base in the way Obama did. And that could also hit turnout.

5. Elections are about change: Every American election is about "change". Clinton has been a part of the national political scene for 30 years. She is regarded as an integral part of the establishment. Trump has promised radical change in many things; a different way of thinking, a new approach to solving problems. He has presented himself as the change candidate. And people may just take the gamble to shake things up, launch the experiment of a new kind of politics with the knowledge they can change things in four years if it doesn't work out.

Reality Check: The truth about the Trump phenomenon

There are other things to consider here. The debates, the first one just over two weeks away, can change the face of the race. Trump is not prepping in the traditional way, with briefing books and mock debates. He, instead, is taking his free-range style to the debate stage, hoping a TV-savvy performance will overwhelm his Democratic opponent and send him surging in the polls.

And there is the "October surprise". Pundits and campaigns always watch for something spectacular popping up in the final weeks. There is an even bigger prospect of that this year with the hacking of the Democratic Party's emails. WikiLeaks, which dumped the first batch just before the Democratic convention, says there is more to come. That could be damaging for Clinton.

A close reading of the polls still suggests Clinton is on course to win the White House.

But this is an election where all perceptions have gone out the window. And Trump has been the biggest beneficiary.